Remember the summer when Citysounds.fm was born during the first Music Hack Day in London? Only a month later, the Citysounds team released a first major update to the mashup before kicking off the work on the iPhone app during the Music Hack Day in Berlin in September.

Today, just a few months later, they’re finally ready to release the much anticipated Citysounds iPhone app. Listen to the sounds of your favorite cities while you’re on the road. We’re so excited and we hope you’re to!

If you don’t know Citysounds yet, it’s one of the most popular applications built on top of the SoundCloud API and lets you stream the latest tracks uploaded to SoundCloud by cities around the world. Sitting in London’s tube, tune in to the hottest tracks from Los Angeles. On the bus in Berlin, discover the sounds of Rio de Janeiro – right from your iPhone.

Here’s what the app will let you do:

Browse and listen to tracks from the most active and popular cities in the world

Locate the city you’re in and listen to the most recent tracks

Give your phone a shake and instantly be transported to a random place

Massive props to the fine Citysounds team for its hard work on both the web and iPhone applications. Oh, and the boys also shared some secrets with us about what’s planned for the next version:

Version 2will let you save your favorite cities, search & browse all cities around the world and it will support social features for easy sharing via Facebook and Twitter.

Oh, and while we’re at it: besides Citysounds, there are two other great applications to browse and discover music on SoundCloud: Tracks On A Map and The Cloud Player – both are also built on top of our API.